Back to EveryPatent.com
| United States Patent |
6,110,016
|
|
Coleman
, et al.
|
August 29, 2000
|
Lens block and method of processing lenses
Abstract
A two-piece lens block allows for the rotation of an edged lens blank in
order to align the cylinder of the lens blank correctly. The lens block
includes a substantially cylindrical base having a first surface facing
the lens blank and an opposed second surface with a plurality of driving
recesses extending into the base from the second surface. A ring member
surrounds the base and includes a mounting surface generally adjacent to
the lens blank. The ring member is rotatable relative to the base prior to
the attachment of the lens blank to the lens block. An edged lens-shaped
cavity is provided in the ring member and provides for nearly full surface
contact of an attachment alloy with a front surface of the lens blank to
alleviate distortion. The two-piece lens block allows edged lens blanks to
be surfaced to finished lenses.
| Inventors:
|
Coleman; Charles R. (Pittsburgh, PA);
Smarto; John E. (Trafford, PA)
|
| Assignee:
|
PPG Industries Ohio, Inc. (Cleveland, OH)
|
| Appl. No.:
|
102324 |
| Filed:
|
June 22, 1998 |
| Current U.S. Class: |
451/42; 451/390; 451/460 |
| Intern'l Class: |
B24B 001/00 |
| Field of Search: |
451/42,43,460,384,390
|
References Cited
U.S. Patent Documents
| Re31897 | May., 1985 | Johnson.
| |
| 2352616 | Jul., 1944 | Canning.
| |
| 2509211 | May., 1950 | Clement.
| |
| 3015196 | Jan., 1962 | Campbell.
| |
| 3049766 | Aug., 1962 | Buckminster.
| |
| 3140568 | Jul., 1964 | Beasley | 51/216.
|
| 3192676 | Jul., 1965 | Buckminster.
| |
| 3271912 | Sep., 1966 | Buckminster | 51/216.
|
| 3448549 | Jun., 1969 | McCall | 51/284.
|
| 3451177 | Jun., 1969 | Buckminster et al.
| |
| 3468366 | Sep., 1969 | Suddarth.
| |
| 3499253 | Mar., 1970 | McCall | 51/277.
|
| 3507076 | Apr., 1970 | Rudd et al.
| |
| 3663983 | May., 1972 | Bole.
| |
| 3704558 | Dec., 1972 | Sarofeen.
| |
| 3994101 | Nov., 1976 | Coburn et al. | 51/216.
|
| 4118898 | Oct., 1978 | Godot | 51/216.
|
| 4149344 | Apr., 1979 | Keane, Jr.
| |
| 4158273 | Jun., 1979 | Olsen et al. | 51/284.
|
| 4287013 | Sep., 1981 | Ronning.
| |
| 5421771 | Jun., 1995 | Wardle | 451/390.
|
| 5462475 | Oct., 1995 | Kennedy.
| |
| 5520568 | May., 1996 | Craighead et al.
| |
| 5669807 | Sep., 1997 | Moreau et al.
| |
Primary Examiner: Eley; Timothy V.
Assistant Examiner: Nguyen; Dung Van
Attorney, Agent or Firm: Mitchell; William C.
Claims
What is claimed is:
1. A method for processing edged lenses comprising the steps of:
placing an edged lens blank on a ring member adjacent a lens-shaped cavity
formed in said ring member, wherein said ring member surrounds a base;
rotating said edged lens blank and said ring member relative to said base
to align said ring member and said base;
attaching said edged lens blank and said base; and
surfacing said edged lens blank to form a finished lens.
2. The method of claim 1 wherein said attaching includes the steps of
injecting an attaching material through said base into said lens-shaped
cavity.
3. The method of claim 1 wherein said edged lens blank is an electro-optic
lens and further including the step of removing said ring after said
attachment of said lens blank and said base and prior to said surfacing of
said edged lens blank.
4. A lens block for mounting a lens blank, said lens block comprising:
a substantially cylindrical base having a first surface facing the lens
blank; and
a ring member surrounding said base, said ring member having a mounting
surface generally adjacent to the lens blank and a lens-shaped cavity
surrounded by said mounting surface, said lens-shaped cavity generally
adjacent to the lens blank, wherein said ring member is rotatable relative
to said base prior to attachment of said base to the lens blank.
5. The lens block of claim 4 wherein said base includes a second surface
opposed from said first surface and a plurality of driving recesses
extending into said base from said second surface.
6. The lens block of claim 5 wherein said base includes a hole extending
from said second surface to said first surface, said hole adapted to
permit an attachment material to be injected therethrough to attach the
lens blank to said base.
7. The lens block of claim 5 wherein three of said driving recesses are
provided in said base and aligned along a diametrical line extending
across said second surface.
8. The lens block of claim 7 wherein said lens block includes a hole
extending from said second surface to said first surface, said hole
adapted to permit an attachment material to be injected therethrough to
attach the lens blank to said base.
9. The lens block of claim 8 wherein said mounting surface includes at
least one slot that extends to a peripheral edge of said ring member.
10. The lens block of claim 9 wherein said ring member includes locating
pins extending from said mounting surface.
11. The lens block of claim 10 wherein said ring member includes an annular
wall opposed from said mounting surface, said annular wall surrounding
said base.
12. The lens block of claim 11 wherein said ring member includes an annular
stop adjacent said lens-shaped cavity, said annular stop abutting against
said first surface.
13. The lens block of claim 4 wherein said mounting surface is
substantially concave.
14. The lens block of claim 4 wherein said ring member includes a plurality
of locating pins extending from said mounting surface.
15. The lens block of claim 4 wherein said mounting surface includes at
least one slot therein and extending to a peripheral edge of said ring
member.
16. The lens block of claim 4 wherein said ring member includes an annular
wall opposed from said mounting surface, said annular wall surrounding
said base.
17. The lens block of claim 4 wherein said ring member includes an annular
stop abutting against said first surface.
18. A lens block for mounting a lens blank, said lens block comprising:
a substantially cylindrical base having a first surface facing the lens
blank and a second surface opposed from said first surface, a plurality of
driving recesses extending into said base from said second surface; and
a ring member surrounding said base, said ring member having a mounting
surface generally adjacent to the lens blank, wherein said ring member is
rotatable relative to said base prior to attachment of said base to the
lens blank.
19. The lens block of claim 18 wherein said base includes a hole extending
from said second surface to said first surface, said hole adapted to
permit an attachment material to be injected therethrough to attach the
lens blank to said base.
20. The lens block of claim 18 wherein said ring member and said base
define a lens-shaped cavity which is shaped substantially the same as the
lens blank and dimensionally smaller than said lens blank.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to ophthalmic lens processing and, more
particularly, to lens blocks for mounting ophthalmic edged lens blanks.
2. Background Information
Eyeglasses commonly utilize lenses having convex outer surfaces and concave
inner surfaces. The two surfaces of each lens have different curvatures to
obtain the desired optical refraction for the lens. For many lenses, the
inner surface is in the shape of a section of a torus. The direction along
which the longer radius is generated is referred to as the cylinder axis
of the lens. These lenses are produced from a circular glass or plastic
lens blank which is subjected to multiple stages of cutting and polishing
on the surfaces. A lens holding chuck, or lens block, is adhered to the
convex outer surface of the circular lens blank, otherwise known as
blocking by techniques known in the art, to prepare the lens blank for
surfacing. See for example, FIG. 1 of U.S. Pat. No. 5,520,568 and the
disclosure associated with that figure (particularly, columns 1-3), which
are incorporated herein by reference in their entirety.
The process of adhering the convex outer surface of the lens blank to the
lens block generally involves placing tape, such as the tape described in
U.S. Pat. No. 4,287,013, to said outer surface, e.g., the finished face of
a semi-finished lens blank. The lens/tape subassembly is attached to the
block by using a low melting temperature alloy. For example, one typical
alloy having a melting point of approximately 117.degree. F. (47.2.degree.
C.) and comprising 45% bismuth, 23% lead, 8% tin, 5% cadmium and 19%
indium can be used. That alloy is injected in liquid form between the
block and the tape and conforms to the convex face of the lens blank.
Presently, it is common to maintain the mounted lens blank on the lens
block throughout the surfacing process to avoid the remounting of the lens
blank on the lens block.
Earlier lens shaping techniques would remove and remount the lens blank on
the lens block at various stages of surface processing. A principal
problem in reattaching the lens blank to the lens block is the proper
alignment of the optical center of the lens blank with the center point
and cylinder axis of the lens block. See, for example, the lens blocks
shown in U.S. Pat. Nos. 2,352,616; 2,545,447; 3,015,196; 3,049,766;
3,192,676; and 4,149,344. Following the surfacing of the lens blank, the
lens/tape subassembly is removed from the lens block by methods known in
the art and the protective tape removed, usually by manually peeling it
off the surface. Thereafter, the peripheral edge of the circular blank is
cut to the final frame or lens shape, which is also known as edging. In
this step, the lens is attached to an edging block by holding mechanisms
known in the art, e.g., U.S. Reissue Pat. No. 31,897, and the peripheral
edge machined to the desired shape for the selected frame.
The use of a low melt temperature alloy to attach the lens blank/protective
tape subassembly to the lens block suffers from certain drawbacks. For
example, the hot alloy can damage the lens, e.g., by cracking a glass lens
or warping a plastic lens. It can also create thermal patterns on the
convex outer surface of a plastic lens, which unless removed, are seen by
the lens wearer as patterns of distortion. Generally, the adhesive or low
melting temperature attachment alloy utilized to attach the lens block to
the lens blank is carefully selected to minimize the foregoing drawbacks.
Certain prior art lens blocks have caused uneven heating of a plastic lens
blank, thereby resulting in the generation of thermal patterns in the
lens. When the thermal patterns are near the edge, they can be removed
from circular lens blanks in the subsequent edging operation. However, if
the marking extends too far into the center of the circular lens blank,
the thermal patterns cannot be removed in the edging operation.
Laminated lenses which include at least two layers of glass or plastic to
form the lens have recently been described. The likelihood of having the
distortion problem discussed above will increase in the case of a
laminated lens, particularly where the convex lens section adjacent to the
lens block is thin. Moreover, there is a tendency for the center of the
laminated lens to be heated higher than the edges by the attachment alloy.
Recently, electro-optical lenses such as electrochromic lenses have been
described. These lenses may be a laminated lens assembly which includes an
electrically activated section of one or more electrically activated
layers between the outer lens layers. Each electrically activated layer is
positioned between two electrically conductive layers, e.g.,
electroconductive metal oxide films. In the construction of the
electro-optical lens, the conductive layers are insulated from each other
to prevent a short circuit, and each conductive layer generally is
provided with a separate lead or contact point for connection to the
controlling electrical circuit. These leads or contact points can only be
easily attached to the conductive layers after the lens has been edged to
its final shape for the selected frame. Alternatively, direct contact to a
bus bar (i.e., without leads) is possible.
In the case of an electrochromic laminated lens, surfacing of the lens
typically occurs after the lens is assembled and the leads or contact
points attached. Conventional lens blocks used with conventional lens
blanks cannot be used with an edged non-surfaced electrochromic laminate
lens, because the support area which has the greatest thermal gradient is
generally within the vision area.
It is an object of the present invention to provide an efficient method for
surfacing edged lens blanks by providing an improved lens block in which
an edged lens blank may be readily and easily attached thereto in an
appropriate aligned position. A further object of the present invention is
to provide a lens block which would provide a sufficiently large contact
area between an attachment material (e.g., a metal alloy, wax or
thermoplastic organic material having an appropriate melting point) and
the front surface of the edged lens blank to avoid patterns of thermal
distortion. Yet another object of the present invention is to provide a
lens block which is easy and economical to manufacture and use.
SUMMARY OF THE INVENTION
The above objects are achieved by a two-piece lens block according to the
present invention. The lens block includes a substantially cylindrical
base and a ring member surrounding the base. The base has a first surface
generally facing an edged lens blank. The ring member includes a mounting
surface generally adjacent to the edged lens blank and a lens-shaped
cavity surrounded by the mounting surface. The lens-shaped cavity is
generally adjacent to the edged lens blank and provides substantially full
surface contact between an attachment material having an appropriate
melting temperature and the edged lens blank to limit or avoid distortion
in the edged lens blank. The attachment material may be a metal alloy, wax
or thermoplastic organic. The ring member is rotatable relative to the
base prior to the attachment of the edged lens blank to the lens block to
allow for proper orientation of the edged lens blank.
The base includes a second surface opposed from the first surface, and the
base may include a plurality of driving recesses extending into the base
from the second surface. The base may be provided with an attachment
supply hole extending from the second surface to the first surface
thereof. The supply hole is adapted to permit an attachment material to be
injected therethrough to attach the lens blank to the lens block.
A portion of the mounting surface of the ring member and a portion of the
first surface of the base may be concave, generally conforming to the
shape of the lens blank. The ring member may additionally include an
appropriate number of locating pins extending from the mounting surface
thereof and a plurality of slots extending to a peripheral edge of the
ring member. The ring member may further include an annular wall opposed
from the mounting surface substantially surrounding the base and an
annular stop abutting against the first surface of the base.
A method of processing a lens blank according to the present invention
includes the mounting of an edged lens blank on the lens block of the
present invention in the proper alignment followed by surfacing of the
edged blank to generate the appropriate optical qualities for the finished
lens. The mounting of the edged lens blank includes placing the edged lens
blank on the ring member adjacent the lens-shaped cavity, aligning the
ring member and edged lens blank relative to the base, and attaching the
lens blank, the ring member and the base together with suitable attachment
material. Once the attachment material has cooled to solidify, the ring
may optionally be removed leaving an attached base and lens block.
These and other objects of the present invention will be clarified in the
description of the preferred embodiments which is described in connection
with the attached figures wherein like reference numerals represent like
elements throughout.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a top plan view of a lens block according to the present
invention;
FIG. 2 is a sectional view of the lens block shown in FIG. 1;
FIG. 3 is a side view of the lens block shown in FIG. 1;
FIG. 4 is a bottom plan view of the lens block shown in FIG. 1;
FIG. 5 is a top plan view of the lens block shown in FIG. 1 with an edged
lens blank attached thereto;
FIG. 6 is a sectional view of the lens block shown in FIG. 5; and
FIG. 7 is a schematic block illustration of the method of processing lenses
according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A lens block 10 according to the present invention is shown in FIGS. 1-6.
The lens block 10 is for mounting of an edged lens blank 5, shown in FIGS.
5 and 6 in phantom, and includes a two-piece assembly which allows for the
rotation of the edged lens blank 5 in order to locate the cylinder of the
lens blank 5 correctly. The edged lens blank 5 may be an electro-optic
lens, e.g., an electrochromic laminate lens assembly, with the leads
attached. This assembly may comprise a laminate of a convex edged lens
blank, an electroconductive layer, e.g., a conductive metal oxide layer,
an electrochromic layer, an ion-conducting layer, a complementary
electrochromic layer, a second electroconductive layer, and a concave
edged lens blank. This lens assembly may comprise a semi-finished lens
blank, e.g., it may be a single or multi-focal lens or other optical
element. The lens block 10 can be formed out of aluminum, however, other
appropriate materials may be utilized to construct the lens block 10.
The lens block 10 includes a substantially cylindrical base 12 with a
generally concave first surface 13 generally facing the lens blank 5. The
base 12 includes three driving recesses 14 extending therethrough from a
second surface 15 opposed from the concave first surface 13 and extending
to the concave first surface 13. As shown in FIGS. 1 and 4, the driving
recesses 14 are along a diametrical line extending across the base 12. The
driving recesses 14 may receive drive studs 9 therein, as shown in FIG. 6,
for attachment to rotating spindles or drives of lens grinding and cutting
machines as known in the art. The base 12 additionally includes supply
hole 16 extending therethrough. The supply hole 16 is adapted to permit an
attachment material 17, shown in FIG. 6, to be injected therethrough to
attach the lens block 10 to the lens blanks 5. Appropriate attachment
materials have a melting temperature of about 120.degree. F., such as the
lead-indium alloy described above. Other suitable attachment materials
include wax or thermoplastic organic material. The base 12 additionally
includes a pair of reference holes 18 extending into the base 12 from the
second surface. As shown in FIGS. 1 and 2, the reference holes 18 do not
extend all the way through the base 12 and stop short of the first surface
13.
A ring member 22 surrounds the base 12 and forms the second piece of the
two-piece lens block 10. The ring member 22 has a concave mounting surface
24 which is generally adjacent to the edged lens blank 5. The mounting
surface 24 of the ring member 22 surrounds a lens-shaped cavity 26 formed
in the ring member 22. The lens-shaped cavity 26 is intended to be
slightly smaller than the edged lens blank 5 and is shaped substantially
similar thereto. The mounting surface 24 of the ring member 22
additionally includes a pair of diametrically opposed slots 28 each
extending from the cavity 26 to a peripheral edge 27 of the ring member
22. The mounting surface 24 additionally may have two pairs of
diametrically opposed locating pins 30 extending from the mounting surface
24. Each locating pin 30 is mounted in a pin hole extending into the ring
member 22.
The ring member 22 includes an integral annular wall 32 which is opposed
from the mounting surface 24 and which surrounds the base 12. An annular
stop 34 of the ring member 22 is adjacent to cavity 26 and abuts against
an outer, substantially planar portion of the first surface 13 of the base
12. The annular stop 34 surrounds an opening 36 which communicates with
the cavity 26.
Another embodiment is envisioned without the annular stop 34 permitting
removal of the ring portion after the attachment material is injected and
cooled to a solid support in the shape of the lens.
In operation, which is shown schematically in FIG. 7, the edged lens blank
5 is placed on the ring member 22 within the locating pins 30 adjacent the
cavity 26. The two-piece lens block 10 of the present invention allows the
rotation of the ring member 22 and lens blank 5 relative to the base 12 to
appropriately align the edged lens blank 5 prior to injection of the
attachment material 17. The lens blank 5 must be aligned relative to the
base 12 because it is already cut to shape, i.e., edged, and the cylinder
to be cut into the lens blank 5 must be aligned properly in the final
lens. Alignment is not an issue in the prior art using circular lens
blanks since during surfacing these have not yet been edged. Alignment of
the lens blank and the lens block becomes an issue where, as in the
present invention, the lens blank 5 is edged prior to surfacing.
Following proper alignment, the attachment material 17 can be injected into
the cavity 26 through supply hole 16 and through opening 36. When
injected, the attachment material 17 is essentially a liquid, as shown in
FIG. 6. The slots 28 will accommodate any discharge such as gas or excess
attachment material 17 as needed. The attachment material 17 quickly
solidifies to attach the lens blank 5, the base 12 and optionally the ring
member 22 together into an integral unit. In an alternative embodiment,
the ring member 22 may be removed after the attachment. As discussed
above, annular stop 34 is not provided in the embodiment where the ring
member 22 is to be removed after attachment. The lens-shaped cavity 26
provides for nearly full contact of the attachment material 17 with the
front surface of the edged lens blank 5 to be heated substantially
equally, thereby alleviating the likelihood of thermal distortion of the
edged lens blank 5. Distortion of the edged lens blank 5 must be avoided
because no further edging of the lens is available. The concave mounting
surface 24 substantially conforms to the shape of the lens blank 5. The
concave inner portion of the first surface 13 conforms to the shape of the
lens blank 5 and provides a substantially uniform thickness to the
attachment material 17 in the cavity 26 which helps maintain even heating
of the lens blank 5. In the embodiments shown in FIGS. 2 and 5, the planar
outer portion of the first surface 13 abutting against the annular stop 34
provides a seal against the attachment material 17. A relatively tight fit
between the outer surface of the base 12 and the annular wall 32 and
between the drive studs 9 and recesses 14 also provides seals against the
attachment material 17.
Following attachment of the properly aligned edged lens blank 5 to the lens
block 10, the edged lens blank 5 will be surfaced to the appropriate
curvature in a conventional fashion using techniques and machinery, such
as a Coburn Model 108 generator, known in the art. As shown in FIG. 4, the
dimensions and configurations of the bottom of the lens block 10 are
designed to fit standard lens surfacing machinery. After the appropriate
curvature is formed in the concave side of the edged lens blank 5, the
lens is finished since it has been previously edged. The finished lens can
be easily removed from the lens block 10 by heating the combined assembly
past the melting temperature of the attachment material 17, which is
generally conducted in a liquid bath. Other methods may be used for
removal of the finished lens such as through a mechanical shock.
This construction allows for easy and proper blocking of an edged lens
blank 5 and permits essentially distortion-free processing of the edged
lens blank 5. This process and apparatus will have particular application
to electro-optic lenses. With this process, edged lens blanks 5 requiring
specific prescriptions to be generated therein can be produced using the
lens block 10 of the present invention. The cavity 26 is specific to one
lens or one frame shape. Consequently, separate lens blocks 10 will be
required for separate lens shapes.
The illustrated embodiments are intended to be representative of the
present invention and not restrictive thereof. It will be obvious to those
of ordinary skill in the art that various modifications may be made to the
present invention without departing from the spirit and scope thereof.
Consequently, the scope of the present invention is intended to be defined
by the appended claims.
Top